protein dimers and even higher oligomers are commonly seen in MALDI,
especially at higher concentrations--even with proteins that are not known
to dimerize in solution. As these are "real" dimers, its hard to call them
artifacts, for instance, they may be induced by the concentration effect of
the drying of the matrix and analyte. In some cases, you can see different
ratios of the monomer/dimer at different areas of the sample spot. You can
minimize them by diluting the sample, and we've also had luck in one case
varying TFA in the protein solution (higher TFA broke up the polymers).
If you want to know if your dimer is real, its best to go to some other
physical analysis technique, such as gel filtration.
Katheryn Resing
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